Orientation selection in distance measurements between nitroxide spin labels at 94 GHz EPR with variable dual frequency irradiation

Tkach, Igor; Pornsuwan, Soraya; Höbartner, Claudia; Wachowius, Falk; Sigurdsson, Snorri Th.; Baranova, T. Yu.; Diederichsen, Ulf; Sicoli, Giuseppe; Bennati, Marina

doi:10.1039/c3cp44415e

Cited by 56 publications

(44 citation statements)

References 28 publications

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“…At present, such studies are performed predominantly using the four-pulse DEER experiment at W-band frequencies recorded for a set of pump and observation positions [49][50][51][52] . Multiple DEER experiments are therefore required, which results in a longer acquisition time than for 2D SIFTER.…”

Section: Epr-correlated Siftermentioning

confidence: 99%

EPR-correlated dipolar spectroscopy by Q-band chirp SIFTER

Doll

Jeschke

2016

Phys. Chem. Chem. Phys.

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While two-dimensional correlation spectra contain more information as compared to one-dimensional spectra, typical spectral widths encountered in electron paramagnetic resonance (EPR) spectroscopy largely restrict the applicability of correlation techniques. In essence, the monochromatic excitation pulses established in pulsed EPR often cannot uniformly excite the entire spectrum. Here, this restriction is alleviated for nitroxide spin labels at Q-band microwave frequencies around 35 GHz. This is achieved by substitution of monochromatic pulses by frequency-swept chirp pulses tailored for uniform excitation. Unwanted interference effects brought by this substitution are analyzed for a pair of electron spins with secular dipolar coupling. Experimentally, the dipole-dipole interaction can be separated from other interactions by a constant-time Zeeman-compensated solid echo sequence called SIFTER. Such SIFTER experiments usually yield a one-dimensional dipolar spectrum. EPR-correlated dipolar spectra can be obtained when the four pulses are replaced by chirp pulses. These two-dimensional spectra encode additional information on the geometrical arrangement of the two spin labels. With the excitation parameters achieved by a home-built Q-band spectrometer capable of frequency-swept excitation, unwanted interference effects can be largely neglected for the examined model compound with a spin-spin distance of 4 nm. The experimentally obtained correlation pattern conforms to the expectation based on the inter-spin geometry of the investigated rigid model compound.

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Section: Epr-correlated Siftermentioning

confidence: 99%

EPR-correlated dipolar spectroscopy by Q-band chirp SIFTER

Doll

Jeschke

2016

Phys. Chem. Chem. Phys.

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“…Unless an optimisation algorithm is applied for this, this task becomes very time consuming and it is not clear whether the solution obtained is unique. In the papers of Abé et al [14] and Tkach et al [32], grid search and sequential quadratic programming optimisation algorithms, respectively, were used for rigid spin systems. For these systems, the number of parameters could be reduced down to three [14] and six [32], respectively.…”

Section: Introductionmentioning

confidence: 99%

Geometric model-based fitting algorithm for orientation-selective PELDOR data

et al. 2014

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Pulsed electron-electron double resonance (PELDOR or DEER) spectroscopy is frequently used to determine distances between spin centres in biomacromolecular systems. Experiments where mutual orientations of the spin pair are selectively excited provide the so-called orientation-selective PELDOR data. This data is characterised by the orientation dependence of the modulation depth parameter and of the dipolar frequencies. This dependence has to be taken into account in the data analysis in order to extract distance distributions accurately from the experimental time traces. In this work, a fitting algorithm for such data analysis is discussed. The approach is tested on PELDOR data-sets from the literature and is compared with the previous results.

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“…PELDOR was also used to measure a series of distances between pairs of Ç labels in DNA (Schiemann, 2009) [56] and pairs of Çm in RNA [57], which were in good agreement with modeled distances. However, the ultimate proof of the non-perturbing nature of nonnatural nucleosides is a high-resolution structure of a duplex containing the modification.…”

Section: Synthesis Of Rigid Spin Labels For Nucleic Acidsmentioning

confidence: 73%